tdf#113694 Fix BreakIterator_CTL surrogate pairs

BreakIterator_CTL in the non CharacterIteratorMode::SKIPCELL mode did
not handle UTF-16 surrogate pairs at all, causing backspace to delete
lone surrogates which is really bad. Just copied the corresponding code
from BreakIterator_Unicode.

Additionally, BreakIterator_th was not correctly skipping non-Thai text
and always treating one character as Thai.

Change-Id: Ia379327e042ff602fc19a485c4cbd1a3683f9230
Reviewed-on: https://gerrit.libreoffice.org/54631Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>

i18npool/qa/cppunit/test_breakiterator.cxx

@@ -919,6 +919,29 @@ void TestBreakIterator::testThai()
         }
         while (nPos > 0);
     }
+
+    // tdf#113694
+    {
+        const sal_Unicode NON_BMP[] = { 0xD800, 0xDC00 };
+        OUString aTest(NON_BMP, SAL_N_ELEMENTS(NON_BMP));
+
+        sal_Int32 nDone=0;
+        sal_Int32 nPos;
+
+        nPos = m_xBreak->nextCharacters(aTest, 0, aLocale,
+            i18n::CharacterIteratorMode::SKIPCELL, 1, nDone);
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Should skip full surrogate pair", static_cast<sal_Int32>(SAL_N_ELEMENTS(NON_BMP)), nPos);
+        nPos = m_xBreak->previousCharacters(aTest, SAL_N_ELEMENTS(NON_BMP), aLocale,
+            i18n::CharacterIteratorMode::SKIPCELL, 1, nDone);
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Should skip full surrogate pair", static_cast<sal_Int32>(0), nPos);
+
+        nPos = m_xBreak->nextCharacters(aTest, 0, aLocale,
+            i18n::CharacterIteratorMode::SKIPCHARACTER, 1, nDone);
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Should skip full surrogate pair", static_cast<sal_Int32>(SAL_N_ELEMENTS(NON_BMP)), nPos);
+        nPos = m_xBreak->previousCharacters(aTest, SAL_N_ELEMENTS(NON_BMP), aLocale,
+            i18n::CharacterIteratorMode::SKIPCHARACTER, 1, nDone);
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Should skip full surrogate pair", static_cast<sal_Int32>(0), nPos);
+    }
 }
 
 #ifdef TODO

i18npool/source/breakiterator/breakiterator_ctl.cxx

@@ -71,8 +71,8 @@ sal_Int32 SAL_CALL BreakIterator_CTL::previousCharacters( const OUString& Text,
         } else
             nStartPos = 0;
     } else { // for BS to delete one char.
-        nDone = std::min(nStartPos, nCount);
-        nStartPos -= nDone;
+        for (nDone = 0; nDone < nCount && nStartPos > 0; nDone++)
+            Text.iterateCodePoints(&nStartPos, -1);
     }
 
     return nStartPos;
@@ -98,8 +98,8 @@ sal_Int32 SAL_CALL BreakIterator_CTL::nextCharacters(const OUString& Text,
         } else
             nStartPos = len;
     } else {
-        nDone = std::min(len - nStartPos, nCount);
-        nStartPos += nDone;
+        for (nDone = 0; nDone < nCount && nStartPos < Text.getLength(); nDone++)
+            Text.iterateCodePoints(&nStartPos);
     }
 
     return nStartPos;

i18npool/source/breakiterator/breakiterator_th.cxx

@@ -127,7 +127,7 @@ void BreakIterator_th::makeIndex(const OUString& Text, sal_Int32 const nStartPos
 
     sal_Int32 startPos = nStartPos;
     while (startPos > 0 && is_Thai(str[startPos-1])) startPos--;
-    sal_Int32 endPos = std::min(len, nStartPos+1);
+    sal_Int32 endPos = nStartPos;
     while (endPos < len && is_Thai(str[endPos])) endPos++;
 
     sal_Int32 start, end, pos;